From the article:
These heavy, rifled weapons are known as “wall guns”, “Amusettes”, (which means a light field cannon), and “rampart guns”, with the word “rampart” meaning a fortification, or embankment, to protect soldiers. They were made as a fill-in between the shoulder arm and cannon. They are approximately five feet in length and weigh in the neighborhood of fifty pounds. The swivel, attached to the stock, enabled the gun to be turned in a 360 degree circle, as well as up and down. The bottom portion of the swivel metal sleeve, or hole, to be fired from a fixed position. Other wall guns, however, have a “spiked” or pointed bottom indicating it can be driven into wood quickly, giving it more mobility. Although these wall guns weren’t used too much during the Revolutionary War, their use was certainly important. The effectiveness of these weapons were attested to when General Charles Lee, writing from Williamsburg in 1776, wrote to Washington that he was obtaining four ounce rifle-amusettes, for they “will carry an infernal distance, the two ounced hit a half sheet of paper 500 yards distant”.